Martensitic Transition Temperature Research Articles

Magnetostriction of Heusler Ferromagnetic Alloy, Ni2MnGa0.88Cu0.12, around Martensitic Transition Temperature

In this study, magnetostriction measurements were performed on the ferromagnetic Heusler alloy, Ni2MnGa0.88Cu0.12, which is characterized by the occurrence of the martensitic phase and ferromagnetic transitions at the same temperature. In the austenite and martensite phases, the alloy crystallizes in the L21 and D022-like crystal structure, respectively. As the crystal structure changes at the martensitic transition temperature (TM), a large magnetostriction due to the martensitic and ferromagnetic transitions induced by magnetic fields is expected to occur. First, magnetization (M-H) measurements are performed, and metamagnetic transitions are observed in the magnetic field of μ0H = 4 T at 344 K. This result shows that the phase transition was induced by the magnetic field under a constant temperature. Forced magnetostriction measurements (ΔL/L) are then performed under a constant temperature and atmospheric pressure (P = 0.1 MPa). Magnetostriction up to 1300 ppm is observed around TM. The magnetization results and magnetostriction measurements showed the occurrence of the magnetic-field-induced strain from the paramagnetic austenite phase to the ferromagnetic martensite phase. As a reference sample, we measure the magnetostriction of the Ni2MnGa-type (Ni50Mn30Ga20) alloy, which causes the martensite phase transition at TM = 315 K. The measurement of magnetostriction at room temperature (298 K) showed a magnetostriction of 3300 ppm. The magnetostriction of Ni2MnGa0.88Cu0.12 is observed to be one-third that of Ni50Mn30Ga20 but larger than that of Terfenol-D (800 ppm), which is renowned as the giant magnetostriction alloy.

Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys

The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.

Theoretical design of Ti2-based magnetic shape memory alloys from first-principles

Magnetic shape memory alloys (MSMAs) typically comprise transition metal and main group atoms. We developed a class of Ti2-based Heusler MSMAs formed by transition metal and metalloid elements using the first-principles calculation method based on density functional theory. For all the studied Ti2YZ (Y = Cr, Mn, Fe, and Co; Z = B, Si, Ge, As, Sb, and Te) Heusler alloys, the calculated formation energies in the austenitic phase show that, except for Ti2CrTe, all alloys have thermodynamic stability. Based on a comprehensive analysis of the total energy difference between austenite and martensite, the density of states (DOS), and the bulk mechanical properties, we predict that of all the Ti2-based alloys studied here, 17 alloys are likely to undergo a martensitic phase transition. The DOS of the cubic structures reveals that the substantial peak structures around the Fermi level, mainly formed by strong hybridization between the Ti atom and its neighbor Y and Z atoms, lead to cubic instability. Compared with the typical MSMA of Ni2MnGa, most Ti2YZ alloys possess a larger martensitic driving force, a higher martensitic transition temperature, and better ductility. Therefore, our study could inspire the development and application of new Ti2-based MSMAs.

Structural transitions and magnetocaloric properties of low-cost MnNiSi-based intermetallics

A series of Mn1-xNi1-xFe2xSi0.95Al0.05 MM’X-type compounds (with x = 0.28, 0.3, 0.32 and 0.35) were investigated for their potential as magnetocaloric materials. Structural and magnetic properties were studied by magnetometry, microscopy and X-ray diffraction. Double substitution of Fe in Mn and Ni sites allowed to tune martensitic transition temperatures between low temperature orthorhombic and high temperature hexagonal structures from 373 K in x = 0.28–183 K in x = 0.35 during cooling. Transition temperatures occur around room temperature for x = 0.30 (300 K for cooling transformation) and 0.32 (270 for heating transformation). Isothermal entropy changes of −8, −19 and −26 J/kg.K were calculated for field changes of μ0H = 0–2, 0–5 and 0–7 T for x = 0.30. The values are comparable to those reported for MnNi(SiAl)-based compounds with single site substitutions (Mn and Ni) by Fe. Further analyses show that high magnetic fields are necessary to induce the magnetostructural transition in all studied compounds, which can be attributed to the presence of secondary phases and/or disorder at a local level.

Investigation on Magnetization, Magnetocalory, Magnetoresistance, and Electric Properties of Ni-Mn Based Heusler Alloy

The magnetic and electrical characteristics of Ni-Mn quinary Heusler alloys are studied in the current work. The results concern the materials’ magnetic and electrical behavior. The physical property measurement system (PPMS) and superconducting quantum interference device (SQUID) were used at various magnetization levels to determine the results. The addition of Fe helps to form the alloy into a smart memory alloy with magnetocrystalline anisotropy, twin border mobility, and varied magnetic and martensite transition temperature characteristics. Character changes in the superparamagnetic (SPM) and paramagnetic (PM) alloys occur between 26 and 34 °C. The curves are supported by the alloy’s martensitic transition temperature change. A large refrigeration capacity is identified in the alloy. These properties are an indication of the alloys’ application prospects. Entropy change helps to detect the inverse magnetocaloric effect in the alloy, whereas adiabatic temperature change helps identify the origin and validity of reverse magnetic properties. The transition temperature changes occur when austenite’s sigma is larger than that of martensite, and as the magnetic field increases, the temperature declines. Isothermal magnetization curves, a large (MR)/B value at low and high magnetic fields, and temperatures near the transformation point suggest that small-crystal Heusler alloys have tremendous promise for low and high magnetic field magnetoresistance applications.

119Sn Mössbauer and magnetization studies of the Heusler alloy Ni2Mn1.48Sn0.52

The results of experimental investigations of the crystal structure, magnetization and Mössbauer spectroscopy of the Heusler alloy Ni2Mn1.48Sn0.52 are reported. The alloy undergoes the martensitic transition from the L21-type cubic structure into 4O-type orthorhombic structure with a thermal hysteresis of ∼23 K. The martensitic transition temperature TM is 309 K. The Curie temperature in the austenitic phase TCA of Ni2Mn1.48Sn0.52 is found to be 316 K. The Mössbauer spectra from the high temperature paramagnetic state at 330 K and the martensitic state at 283 K were both singlets, showing a typical paramagnetic feature in the narrow temperature range just below TM. With further decrease of temperature, the ferromagnetic ordered state also appears in the martensitic phase. The Curie temperature in the martensitic phase TCM is found to be 256 K. Furthermore, the exchange bias effect is observed in the temperature range 1.8 K ≤ T ≤ TB (∼130 K), where TB is an exchange bias blocking temperature. The values of a hyperfine magnetic field at Sn nuclei of Ni2Mn1.48Sn0.52 fall significantly below the molecular magnetic field approximation for S = 1. On the basis of the experimental results, the electronic and magnetic properties of Ni2Mn1.48Sn0.52 are discussed.

Theoretical investigation of phase transitions in the shape memory alloy NiTi

There remain a few unsolved problems when the ab initio approach was applied to study one of the most important binary shape memory alloys (SMAs), NiTi (nitinol), which is the starting material for alloying numerous multicomponent SMAs. This hinders the computational design of complex SMAs with desirable properties. In this Letter we report that including the electronic free energy in the Gibbs free energy nearly reduces by half the large errors in previously predicted martensitic transition temperatures, and the controversy on the ground state of NiTi is resolved by reaching the convergence in free-energy calculations. In addition, the present results demonstrate that the martensitic transition path in stoichiometric NiTi is directly from B2 to $\mathrm{B}{19}^{\ensuremath{'}}$ without intermediate phases.

Microstructure, phase transformation and mechanical properties of NiMnGa particles/Cu composites fabricated by SPS

Microstructure, phase transformation and mechanical properties of NiMnGa particles/Cu composites prepared by spark plasma sintering method were investigated by SEM, EDS, XRD, susceptibility measurements and mechanical tests. The NiMnGa particles were found to react with Cu matrix and the composites exhibited a similar crystal structure to the Cu matrix. The martensitic transformation and Curie transition of the composites were weakened due to the composition change of NiMnGa particles caused by reactions. With increasing NiMnGa particles content, the martensitic transformation and Curie transition of the composites were enhanced to some extent. However, the martensitic transformation temperature and Curie transition temperature were decreased by ~50 K as compared to those of the original NiMnGa particles. The compressive strength of the composites increased with the increase of NiMnGa particles content, whereas the compressive strain was decreased gradually.

Surface quality and morphology of NiTiCuZr shape memory alloy machined using thermal-energy processes: an examination of comparative topography

Adding alloying elements like copper (Cu) and zirconium (Zr) to binary NiTi shape memory alloys (NiTiCuZr SMA) raises the martensitic transition temperatures and functional fatigue properties while maintaining high corrosion and wear resistance. Therefore, it is essential to make high-precision SMA components with less damage to be machined into various complex shapes, sizes, and surface topographies to meet the needs of several engineering applications. In this research work, advanced machining processes like wire electrical discharge machining (WEDM) and fiber laser machining were employed to machine NiTiCuZr SMA and study their processing parameters’ effects on the surface roughness, topography changes, and surface hardness. 3D surface topography and surface roughness on the machined surfaces were evaluated through contact and non-contact measurement techniques. The differential scanning calorimetry (DSC) test was conducted on the NiTiCuZr SMA before and after machining to confirm changes in the shape memory properties. When both processes were used at high energy levels, the formation of the resolidified layer and surface defects were more pronounced, increasing surface roughness. DSC curves for heating and cooling profiles show similar transformation temperatures for WEDM and laser machined NiTiCuZr SMA. On comparing two different machining processes, the WEDM process resulted in the Ra (μm) being 28.2% lower, the surface topography was smooth, and the microhardness was 11.9% lower than the samples machined using laser machining. This shows that machining of NiTiCuZr SMA using WEDM gives a better surface finish, reaching a fair decision that WEDM is a better alternative to laser machining.

Room temperature giant magneto-caloric effect in Ni45Mn44Sn11-XInX (X = 1, 3) disordered Heusler alloy: The role of martensite transition

Here, we report the first order martensite to austenite transition characterized through magnetic and calorimetric studies in (off-stoichiometric) shape memory Heusler alloy Ni45Mn44Sn11-XInX (X = 1; 3) in the proximity of room temperature. The structural properties of the alloys were checked with x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and energy dispersive x-ray analysis (EDXA). The dominance of a particular phase (martensite or austenite) at room temperature can be predicted from the structural study by XRD as two different phases (L21 and 10 M) were found at room temperature with different proportion for the two alloys. Martensite transition was observed near the room temperature for both samples which was monitored with differential calorimetry and magnetization study. A large magneto-caloric effect was found in the system near the room temperature observed from the magnetic measurements. The calculated entropy change (3.24 JKg−1K−1 and 11.2 JKg−1K−1 for X = 1 and 3 respectively) and the refrigerant capacity (27 JKg−1 and 40 JKg−1 for X = 1 and 3 respectively) for 3 T magnetic field were found to be significant for practical applications near room temperature. A small amount of In substitutions in Sn sites have influenced the martensite transition as a significant increase in the martensite transition temperature has been observed. The magnetocaloric effect in these materials has been understood in the realm of sharp magnetization change arising in the vicinity of metamagnetic transition from the martensite phase (weakly magnetic) to the austenite phase (ferromagnetic). The In substitution is thought to influence the hybridization between Ni-Mn bonds which in turn influence the martensite transition and thereby enhancing the magnetocaloric property of the materials.

Anomalous heat transfer near the martensite-austenite phase transition in Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys

The paper presents a detailed investigation of the thermal transport of the Ni50Mn28Ga22-x(Cu, Zn)x (x = 0; 1.5) alloys through specific heat, thermal diffusivity and thermal conductivity measurements. It is shown that the partial replacement of Ga atoms by Zn or Cu atoms leads to a convergence of magnetic and martensitic phase transition temperatures. Our measurements of the thermal diffusivity and thermal conductivity revealed that the behavior of these parameters in the phase transitions region is anomalous due to the coexistence of martensite-austenite phases and the effect of the latent heat of the phase transition. Moreover, the latent heat plays a crucial role in the appearance of a deep minimum of thermal diffusivity in the region of martensitic transformation for the Cu- and Zn-doped samples. Estimates of the phonon mean free path lph in martensitic and austenitic phase gave values of lph,mart = 1.5 nm and lph,aust = 1.9 nm, respectively. This implies that the main mechanism of phonon scattering is local structural inhomogeneities, which decrease sharply upon transition from martensite phase to the highly symmetric austenitic phase.

Preparation of porous TiNi-Ti alloy by diffusion sintering method and study of its composition, structure and martensitic transformations

The study demonstrates a method for controlling not only the phase composition but also the atomic composition of TiNi matrix in porous TiNi-Ti alloys developed for biomedical uses as implants. The alloys were obtained from TiNi powder which was sintered with Ti powder added at as much as 0–10 at%. The structure, phase and chemical composition of the produced TiNi-Ti alloys was investigated with respect to the amount of Ti added into the material. It is shown that in the sintered product containing 5 at% and more of Ti additive, the composition of its TiNi matrix becomes close to equiatomic (with Ti:Ni atomic ratio ~1), and the excessive Ti precipitates as secondary phases Ti2Ni and Ti3Ni4. In parallel, with increase in Ti additive from 0–10 at%, the structure of the precipitating Ti2Ni type phases changes its morphology from separate spherical or pyramidal precipitates to large dendritic formations. The direct martensitic transformation from austenite to martensite in all the samples was found to proceed in two stages and through the R-phase (B2→R→B19′). Thermoresistive analysis demonstrated that TiNi-Ti samples with 5 and more at% of Ti had their characteristic starting temperature of martensite transition stabilizing at ~57 °C (330 K). This implies that the sample with 5 at% of Ti additive exhibited desired martensite transition temperatures, while containing a minimum concentration of secondary-phase precipitates in its matrix which deteriorate its properties. Thus, for the first time, we show that a very simple preparation approach based on sintering powders of TiNi and Ti is capable of producing porous TiNi-Ti alloys with properties optimized for fabricating bone implants.

Doping site induced alteration of incommensurate antiferromagnetic ordering in Fe-doped MnNiGe alloys

The magnetic structure of Fe-doped MnNiGe alloys of nominal compositions ${\mathrm{MnNi}}_{0.75}{\mathrm{Fe}}_{0.25}\mathrm{Ge}$ and ${\mathrm{Mn}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{NiGe}$ has been explored through detailed neutron powder diffraction (NPD) study in ambient and high-pressure (6 kbar) conditions. Both these alloys crystallize with ${\mathrm{Ni}}_{2}\mathrm{In}$-type hexagonal structure (with $P{6}_{3}/mmc$ space group) at room temperature and undergo a martensitic transition to low-temperature TiNiSi-type orthorhombic structure (with space group $Pnma$). Both the alloys show incommensurate antiferromagnetic ordering at the low-temperature martensitic phase. However, the modulation of the magnetic structures depends strongly on the doping site of Fe. The incommensurate propagation vector $\mathbf{k}$ for ${\mathrm{MnNi}}_{0.75}{\mathrm{Fe}}_{0.25}\mathrm{Ge}$ and ${\mathrm{Mn}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{NiGe}$ alloys are found to be (0.1790(1),0,0) and (0.1543(3),0,0), respectively at 1.5 K, and these remain almost unchanged with increasing sample temperature under ambient conditions. The application of the external pressure results in a significant effect on both martensitic transition temperature and low-temperature magnetic structure. The propagation vectors $\mathbf{k}$ for both the alloys show a monotonic decrease with increasing sample temperature in the presence of external pressure. Interestingly, no sign of the magnetically ordered hexagonal austenite phase was observed in any alloys down to the lowest measurement temperature.

Exchange Bias Effect in NiMnSbB Ferromagnetic Shape Memory Alloys Depending on Mn Content

In this study, exchange bias effect was investigated in boron added NiMnSb Heusler alloys. The samples were fabricated by arc melting method with Ni49Mn37,5Sb13,5+Bx, Ni49Mn37,7Sb13,3+Bx and Ni49Mn37,9Sb13,1+Bx nominal compositions. XRD analyzes showed that the samples were in L21 crystal structure at room temperature. While the martensitic phase transition temperatures increased, the magnetic moment value decreased with the increase in Mn content. The decrease in magnetization is owing to the increase in antiferromagnetic interactions with the increase of Mn content. Under low field and zero field cooling M-T measurements revealed that antiferromagnetic interactions were more dominant at low temperature but ferromagnetic behavior was more effective in the system at high temperature region. The coexistence of ferromagnetism and antiferromagnetism in a magnetic material can cause the exchange bias effect. Therefore, the hysteresis loops were examined at 5 K of the samples cooled under 50 kOe magnetic field. The shift at the origin of the magnetization curve, which is attributed to the exchange bias effect, increased with increasing Mn amount.

Magnetism and transport behavior of Ni42Co8Mn38Sb12: Magnetization, electrical resistivity and Hall effect measurements

Magnetic and transport behavior of Ni42Co8Mn38Sb12 alloy is discussed using the combined results of magnetization, electrical resistivity and Hall effect measurements. The alloy undergoes a ferromagnetic transition at 364 K, followed by a martensitic transition at 110 K. Large positive Curie-Weiss temperature, soft-ferromagnetic behavior with negative magnetic entropy change below 50 K and a well-scaled normalized magnetic-entropy onto a single universal curve confirm the predominant ferromagnetic exchange interactions in the alloy. Normal Hall coefficients were found to be nearly constant in ferromagnetic region in the temperature range of 120–300 K. The electrical transport properties are largely governed by electrons with a carrier concentration of about 1023/cc. Quadratic dependence of anomalous Hall resistivity (ρxy) on longitudinal resistivity (ρxx) indicates the dominant intrinsic contribution. In a magnetic field of 50 kOe, magnetoresistance is found to be about 34% near the martensitic transition temperature while it is about 2.8% near the second-order transition.

Magnetic properties, martensitic transformations and magnetocaloric performances in Ni44Mn45-xFexSn11 (x = 0–3) Heusler alloys

The structural, magnetic, and magnetocaloric properties of Ni44Mn45-xSn11Fex (x = 0, 1, 2 and 3) Heusler alloys have been studied detailly by means of X-ray diffraction, differential scanning calorimetry, and magnetization measurements. The martensitic transition temperature (TM) and austenite Curie temperature (TAC) increase gradually with increasing Fe content. Large differences in magnetization between the ferromagnetic austenite and weakly magnetic martensite phases and obvious thermal hysteresis have also been observed during the martensite transformation. With the magnetic field change up to 0–7 T, the maximum value of magnetic entropy changes reaches 26.7 and 23 J kg−1K−1 for x = 1 and 2, respectively, which are much larger than the undoped sample (9.8 J kg−1K−1). Whereas, the effective refrigerant capacity RCeff reduced due to Fe doping increased the hysteresis loss. The alloy for x = 1 has highest RC value of 172 (255) J kg−1 for a magnetic field change of 0–5 T (0–7 T), furthermore, a large magnetic entropy change and moderate RCeff has been obtained around room temperature.

Randomly packed Ni2MnIn and NiMn structural units in off-stoichiometric Ni2Mn2−yIny alloys

${\mathrm{Ni}}_{2}{\mathrm{Mn}}_{2\ensuremath{-}y}{\mathrm{In}}_{y}$ alloys transform from the martensitic $L{1}_{0}$ antiferromagnetic ground state near $y=0$ to the austenitic ferromagnetic $L{2}_{1}$ Heusler phase near $y=1$ due to doping of In impurity for Mn. The off-stoichiometric alloys prepared by rapid quenching are structurally metastable and dissociate into a mixture of $L{2}_{1}$ (${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{In}$) and $L{1}_{0}$ (NiMn) phases upon temper annealing. Despite this structural disintegration, the martensitic transformation temperature remains invariant in the temper annealed alloys. Investigations of the local structure of the constituent atoms reveal the presence of strongly coupled ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{In}$ and NiMn structural units in the temper annealed as well as the rapidly quenched off-stoichiometric ${\mathrm{Ni}}_{2}{\mathrm{Mn}}_{2\ensuremath{-}y}{\mathrm{In}}_{y}$ alloys irrespective of their crystal structure. This random packing of the $L{2}_{1}$ and $L{1}_{0}$ structural units seems to be responsible for invariance of martensitic transition temperature in the temper annealed alloys as well as the absence of strain glass transition in rapidly quenched alloys.

Pressure study of magnetism in off-stoichiometric Ni2MnSn-based alloys

Pressure study of the Heusler Ni2MnSn-based alloys revealed divergent values of the pressure effects on magnetic properties within a group of the off-stoichiometric alloys. An increase in temperature of the structural martensitic transition in the Mn-rich alloys under pressure is adequate for volume changes that accompanied the structural transition. An anomalous decrease of electric resistivity of the alloys in vicinity of the structural transition verifies a transfer into ferromagnetic order of the alloys above the transition temperatures. Almost no changes of exchange-spring and exchange-bias effects were detected under pressure in all the studied alloys. All the observed pressure effects are discussed with help of recent quantum-mechanical calculations of effects of multiple point-defects on magnetism of stoichiometric Ni2MnSn alloy.

Correlation of magnetocaloric effect through magnetic and electrical resistivity on Si doped Ni–Mn–In Heusler melt spun ribbon

The effect of chemical substitution of Si on Mn site in Ni47Mn40-xSixIn13 (x = 1, 2 & 3) melt spun ribbons on the structure, electrical, magnetic and magnetocaloric studies are investigated. All the synthesized ribbons exhibits austenite phase at room temperature. It is found that the increase of Si content under applied magnetic fields of 0.05 T and 5 T shifts both the Curie transition temperature of the austenitic phase (TCA) and martensitic phase transition temperature (TM) towards lower temperatures. The splitting of ZFC and FC curve during magnetic measurements exposes exchange bias phenomenon attributed to irreversibility nature of magnetization due to inhomogeneous magnetic anisotropy below the blocking bias temperature. The large magnetic entropy change (ΔSM) is observed across the martensite transformation and a maximum magnetic entropy change (ΔSM)max of 10 Jkg−1K−1 is obtained for x = 1 ribbon at 273 K with a magnetic field change of 5 T. Upon further increase of Si content, the (ΔSM)max values are found to decrease from 6.3 Jkg−1K−1 (x = 2) to 5.54 Jkg−1K−1 (x = 3) and the same trend is observed for ΔSMm-ρ values.

Spinodal decomposition in ternary Mn-Cu-Cr alloy and its influence on martensitic transition temperatures

The effect of partial substitution of Cu by Cr on the spinodal decomposition of face-centered cubic (f.c.c.) austenite in the as-quenched Mn-10Cu-4Cr alloy is studied after different ageing treatments by small-angle neutron scattering (SANS) and in situ neutron diffraction. Under the same quenching conditions, additional α-Mn phase with A12 structure in the Mn-10Cu-4Cr alloy is observed as compared with Mn-13Cu alloy at room temperature (RT). The replacement of Cu atoms by Cr atoms retards the spinodal decomposition of austenite during ageing compared to the binary Mn-13Cu alloy according to SANS and Differential scanning calorimetry (DSC) results. The reason is that Cr enriches in the α-Mn phase, and thus its addition leads to the formation of the α-Mn phase. Compared to the Mn-13Cu alloy, there is an increase in the tetragonality of the face-centered tetragonal (f.c.t.) martensite, which may be attributed to changes in magnetic interaction owing to partial substitution of Cu by Cr. The higher tetragonality value leads to a higher volume effect during martensitic transition (MT) of Mn-10Cu-4Cr alloy than that of Mn-13Cu alloy (around 1.5 times). The lattice parameters of the f.c.t.-martensite do not converge exactly to the parameter of the f.c.c.-austenite at the MT temperature due to replacement of Cu by Cr. Instead, there is a jump of the lattice parameters during phase transition.